Includepath fix for libmythdvdnav build failure

Description

After upgrading to Qt 4.5.2, mythtv build failed with the following errors:

dvdnav/dvdnav.c:36:27: error: dvdnav/dvdnav.h: No such file or directory
dvdnav/dvdnav.c:37:32: error: dvdread/dvd_reader.h: No such file or directory
dvdnav/dvdnav.c:38:31: error: dvdread/nav_types.h: No such file or directory
dvdnav/dvdnav.c:39:50: error: dvdread/ifo_types.h: No such file or directory

Looking at dvdnav.c (and other source files in libmythdvdnav), the includes are indeed defined inconsistently and not fully resolved in the .pro file. For example, in dvdnav.c:

36: #include "dvdnav/dvdnav.h"
40: #include "remap.h"

Yet both files are in the same directory (libmythdvdnav/dvdnav).

The attached patch fixes this problem by explicitly adding '.' to the INCLUDEPATH in libmythdvdnav.pro.